Deflecting Asteroids with Paint

schnippy writes: "Researchers at the University of Arizona have calculated that small earth-crossing asteroids can be deflected by "coating them with a layer of white paint or dust." This finding won't be of much help against the larger doomsday asteroids (like the recently discovered 1950 DA) but it will help deflate military proposals to use nuclear weapons to deflect potentially hazardous asteroids."

Comments

Asteroids, I used to play that game...

[gnovos]

Why does everyone whine about nuking asteroids? Why NOT nuke them? Even the really big ones? Even the ones that people say are "the size of Texas"? And I don't mean the "try one nuke and give up" that they do in the movies right before sending the poorly trained oil rig workers. I mean rain down thousands, if not tens or hundreds of thousands, of 150 megaton nukes. Turn that whole nasty blob of metal and rock into white hot hell-fire plasma. Not only would it be fun and pretty, but we'd also get to empty out all the really nasty big mother nukes that have been sitting around and collecting dust forever.

Re:Asteroids, I used to play that game...

[Perdo]

Let's see, we want to turn the entire thing into plasma, which I guess could arbitrarily be 10,000 degrees centigrade. Let's ssume it takes one calorie to raise 1 gram of stuff one degree celcious. Now we run our wizzard on a sphere the size of texas, with moon equvalent composition.

about 1.685 x 10^45 gram-calories needed

1 Kiloton TNT equals 1 x 10^12 gram-calories

Approximatly 1.68491109264290913984 x 10^32 Kilotons of TNT needed to convert our texas sized asteroid into 10,000 degree celcious plasma.

I'm going to step out on a limb and make the wild guess that we don't have 16,849,110,926,429,091,398,400,000,000 Megatons worth of nuclear devices.

In fact, It would take the sun 33 years to produce that much energy.

I think I miscarried a decimal somewhere but only being off by a magnitude of 10 is moot on the scales we are talking. suffice to say we could push it around, if we caught it early, but turning the entire thing into plasma is not an option.

Unless we used the mars' atmospheric lazing affect to concentrate a gamma ray lazer created by letting Phobos meet anti-Phobos...

The only question is, where do we get anti-Phobos from? heh..

Re:Asteroids, I used to play that game...

[Mr.Intel]

Put the abacus and crack pipe down. Step away from the crack pipe... You have *way* too much freaking time on your hands dude.

Re: Rate of change

[Raetsel]

Interesting choice...

1. A small rate of change over a very long time

   (OR)

2. A rapid change close to the point when change is needed

We see these types of things happen all the time -- notably on 'real life' cop shows. Either you steer early and avoid an obstacle, or you yank the wheel at the last second, lose traction, and skid into oblivion anyway.

I'll take the first choice, thanks. That way we can know earlier whether it's working or not, and take extra steps if necessary.

Re: Rate of change

[Perdo]

I fully agree, but since an asteroid's orbit cannot be accurately predicted to "earth hit or miss" accuracy greater than about 20 years in advance, that little nudge may be the nudge that causes the asteroid to hit instead of miss. Strapping one of these magnetic bubble solar sails would alter an asteroid's orbit so drasticly, even on late notice, and be steerable to boot, that they make painting the surface white pale by comparison (pardon the pun).

Same theory, more active approach and to paint it would still require a launch, intercept, and application of device, be it paint or a giant magnetic field. The best part is a system like this could be used to steer an earth crosser into earth orbit, providing plenty of zero G raw materials for future missions.

Re: One (slightly used) asteroid

[Raetsel]

• "...zero G raw materials for future missions."

Or... a counterweight for a space elevator!

I suppose the longer we wait, the more stuff we can take -- it'll take less fuel to get there. (Unless we're using antimatter propulsion in 850 years or so... then I guess it really wouldn't matter.)

Re: One (slightly used) asteroid

[Perdo]

God, I like how you think, even if we are on different sides of the T(H)GSB fence.

What he is talking about folks, is the bigger the counterweight, The bigger payload your space elevator could carry, without needing a thicker teather toward the top. Also it enables construction by lowering strings from orbit, because there is something nice sized in orbit to teather to. This is especially important for the first strand, that will be too weak initially to support any weight at all, and certainly not the weight of an entire other strand.

Re:Chaos Intervenes

[Perdo]

1) the mass of the object is know

The mass of an asteroid is not known. 433 Eros, which we know better than any other asteroid, still has an unknown mass for purposes of calculating it's orbit 800 years into the future. Being off by even a few grams results in being off by thousands of miles in final trajectory. It's apparent mass is between 6.69 and 7.2 x 10^15 kg enough to put our calculations off by entire solar units, after 800 years have passed. There is also the problem of asteroids constantly shedding and gaining mass due to collisions, dust deposition and even the solar wind itself depositing dust or blowing deposited dust away.

2) the sice of the surface is known

"Sice" is an Ceske (Check) word that I assume means reflectivity. Consider this: look at a common crystal. Notice that it's reflectivity is determined by it's orientation to the veiwer. The moon always presents the same face to earth, but the sun "gets to see" all sides of the moon. If we base our calculations of an objects reflectivity on observations from earth, or a spacecraft orbiting the asteroid, we cannot make accurate calculations of the objects reflectivity because only one set of data really matters, the reflectivity of the object from the sun's point of view, which may also be variable.

3) the orbit(distance) is known

The orbit can be guessed. We can know with relative certainty where an object was. We can know fairly accurately where it will be in 20 years. We can wildly speculate where it will be in 800 years. Consider the cesium beam atomic clock. It is accurate to 1 x 10^-17 seconds. Such a clock would be off by as much as a thousandth of a second in 800 years. Given that deviation, Calculations of an orbit could be off by several kilometers just on un-guessable timing errors alone. Unfortunately, there is a mathematically unsolvable problem too: The Three-Body Problem, well explained here. Unfortunately, we are faced with a 32 body problem, just counting the sun, planets and major moons. It doesn't even end there. The mass of any body is not consistent across it's surface. For instance, there are places on the earth that "pull" harder than others. This is well mapped on earth, and there are satellite launches planned or in orbit to more closely map this phenomenon, but we have just barely scratched the surface as far as research into, for instance, Jupiter's Local gravitational variations, which have a much greater impact on solar orbit calculations than any body in the solar system.

4) the intensity of sunlight is known

The intensity of sunlight is unknown. The sunspot activity cycle causes the solar wind to change in intensity. Additionally, it warms and cools cyclically. I've heard on a ten thousand or so year cycle, but I cannot remember the source. The sun is also very gradually warming due to the natural life cycle of stars. The planet's magnetic field's slow and accelerate the solar wind and create airfoil shaped shadows in their wakes, through which asteroids must pass. The Planet's magnetic fields also have a quite variable affect on the solar wind, as watching an aurora will show you.

I'll leave you with this:

You can watch a wave sweep the beach and know that the beach will likely have the same shape after its passing but to predict with certainty where a particular grain of sand will go is not within our abilities and never can be.

There are many waves, and even they affect the orbits of asteroids, as the friction of tides moved the moon out to it's current orbit, and slowed the earth to it's present length of day.

Care to guess the coefficient of friction of metallic-hydrogen against it's unknown but assumed "rocky" core? Tidal forces within Jupiter will have to be factored in too.

Just to many variables.